Results from US clinical trials into a heart failure drug have shown it was an amazing success.

But BiDil will not to be remembered for its effectiveness.

Instead, it is set to become one of the most controversial drugs ever as it is targeted solely at black Americans.

The treatment, which is a combination of two existing drugs, isosorbide dinitrate and hydralazine, was initially tested more than 20 years ago on white and black populations but was not thought effective enough to take forward.

But the latest trials, involving more than 1,000 African Americans, were stopped early in July because it was so successful.

NitroMed, the company behind the drug, revealed on Monday the drug improved survival rates by 43% compared to standard treatment.

It now seems likely the US Food and Drug Administration (FDA), the country's regulatory body, will grant the drug a licence when it comes up for consideration next year.

'Ethnic drug'

The drug, which is administered orally, has already caused controversy on both sides of the Atlantic as it would become the world's first "ethnic drug".

But while the marketing and development of the treatment has been branded as crude, experts say it actually represents a step towards genetically-targeted drugs.

It has been known for some time that certain ethnic groups are more prone to some diseases than others.

In the US African Americans are twice as likely to develop heart failure than white people.

A similar pictures emerges in the UK with certain ethnic groups more susceptible to disease than others.

As a GP I would be angry if I was told you can prescribe this drug to these people but not those, that is just not fair

Dr Jim Kennedy, of the Royal College of GPs

The latest government Health Survey for England showed that South Asian men were more at risk of angina and heart attack than other groups.

Black Caribbean and Indian men were at greater risk of stroke and all ethnic minority groups, apart from the Irish and Chinese, were likely to suffer a higher rate of diabetes.

Conversely, other evidence has suggested the white population is more prone to cancer.

Doctors are also realising that certain groups respond better to some treatment.

For example, black heart patients are known have a poorer response to beta-blockers and Ace inhibitors, both of which are used to treat heart disease.

In this context, Professor Mark Johnson, a lecturer in diversity in health and social care at De Montfort University in Leicester, welcomed BiDil.

'Not effective

"I think it is probably a positive thing to develop treatments to meet specific needs of certain populations.

"Some of the favoured medicine, especially for heart disease, is not always effective.

"Any GP worth their salt will assess a patient and try them on drugs they think will work with their genetic make-up."

But he said the problem with BiDil is that it "looks like a racialised drug and that raises all sorts of concern".

"Race is the lazy man's way to get a genetic marker. Genetic markers are not necessarily easily reflected as a visible marker.

"But the concept of different treatment for different people is not new. After all, men and women are treated differently as are children in comparison to adults."

There is concern that some populations - the poorer ones - will be neglected in drug development

Dr Helen Wallace, of GeneWatch

A NitroMed spokeswoman said if granted a licence the drug, which works by restoring depleted nitric oxide levels, should be welcomed.

"The trials, and indeed earlier trials, showed it had a significant impact on treating heart failure among African Americans."

And she defended the decision to only test the drug in these trials on black people, saying that was decided after discussions with the FDA.

However, Dr Jim Kennedy, prescribing spokesman for the Royal College of GPs, said it would be "totally wrong" if BiDil was licensed solely for black people.

"As a GP I would be angry if I was told you can prescribe this drug to these people but not those, that is just not fair.

Genetics

"All licensed medicine should be available to all people."

But he said it was only right that doctors try to work out how a person's genetic make-up would affect treatment.

"We know variations exist and GPs make a reasonable guess at working out a person's genetics using background, exercise, diet, experiences on other medications as well as skin colour.

"The problem is that at the moment we are no where near good enough."

But he said that would all change with developments in DNA, which could potentially allow doctors to identify which treatments patients would respond best to.

The Medical Research Council, funded by the government to promote research, said such developments were extremely promising for patients.

South Asians in Britain are more susceptible to heart attacks

A spokeswoman said: "The more specifically we can treat an individual for their particular ailments, theoretically the more effective treatment should be.

"We are steadily working towards more personalised medicine and recent advances such as mapping the genome, the promise of stem cells and large population studies that combine research into genetics, lifestyle and environment are opening up the potential for a more tailored approach."

But not everyone is convinced. Dr Helen Wallace, deputy director of GeneWatch, a not-for-profit group that monitors developments in genetic technologies, remains sceptical about the merits and accuracy of genetically-targeted drugs.

She said BiDil was a "worse than crude" attempt to define humans in genetic groups.

"Racial differences are not really understood.

"There are more genetic differences within ethnic groups than between them. It is questionable whether there is a genuine biological difference."

And she said even more sophisticated approaches to genetics were dubious.

"There is concern that some populations - the poorer ones - will be neglected in drug development.

"And it is a question of complexity. Environmental factors also play a role in an individual's response treatment and the danger is that too much emphasis can be placed on genes."